Which is the better fighter, P-40F or Typhoon?

[Schweik]

You are, of course, joking.

I have seen some old books published during the war that claim the P-40 could do over 400mph in level flight (and not the Q).

And I've seen plenty claiming that the P-40 was "unmaneuverable and slow but rugged" so what?

Nope, not joking. I have no reason to assume that video is made up. They routinely dove to over 500 mph TAS including in training - the English noted this early on with the Tomahawk. I doubt many combat pilots pushed the limits as far as the two tests mentioned in the video (as it would be extremely risky) but they could if they had to. The risk would be to pass the sound barrier in a dive, same as with a P-51 or P-47 etc.

Just because you don't understand it doesn't negate it.

 

[Shortround6]

And I've seen plenty claiming that the P-40 was "unmaneuverable and slow but rugged" so what?

Nope, not joking. I have no reason to assume that video is made up. They routinely dove to over 500 mph TAS including in training - the English noted this early on with the Tomahawk. I doubt many combat pilots pushed the limits as far as the two tests mentioned in the video (as it would be extremely risky) but they could if they had to. The risk would be to pass the sound barrier in a dive, same as with a P-51 or P-47 etc.

Just because you don't understand it doesn't negate it.

AIr speed indicators were notoriously unreliable at higher than normal speeds. Many planes 'recorded' some astonishingly high dive speeds in WW II

Just for laughs figure it out. 661 mph at 5,000ft (got to leave room to pull out ) is Mach .884 at 10,000ft it is mach .899

From wike so......
on the Spitfire. ......

Beginning in late 1943, high-speed diving trials were undertaken at Farnborough to investigate the handling characteristics of aircraft travelling at speeds near the sound barrier (i.e., the onset of compressibility effects). Because it had the highest limiting Mach number of any aircraft at that time, a Spitfire XI was chosen to take part in these trials. Due to the high altitudes necessary for these dives, a fully feathering Rotol propeller was fitted to prevent overspeeding. During these trials, EN409, flown by Squadron Leader J. R. Tobin, reached 606 mph (975 km/h) (Mach 0.891) in a 45° dive.


In April 1944, the same aircraft suffered engine failure in another dive while being flown by Squadron Leader Anthony F. Martindale, Royal Air Force Volunteer Reserve, when the propeller and reduction gear broke off. The dive put the aircraft to Mach 0.92, the fastest ever recorded in a piston-engined aircraft, but when the propeller came off, the Spitfire, now tail-heavy, zoom-climbed back to altitude. Martindale blacked out under the 11 g loading, but when he resumed consciousness, he found the aircraft at about 40,000 feet with its (originally straight) wings now slightly swept back.[125] Martindale successfully glided the Spitfire 20 mi (32 km) back to the airfield and landed safely.[126] Martindale was awarded the Air Force Cross for his exploits.[127]

RAE Bedford (RAE) modified a Spitfire for high-speed testing of the stabilator (then known as the "flying tail") of the Miles M.52 supersonic research aircraft. RAE test pilot Eric Brown stated that he tested this successfully during October and November 1944, attaining Mach 0.86 in a dive.


Then look at all the troubles the P-38 and even the P-47 had with mach tuck.

or from Bill Marshall:
The fastest I Have ever heard of a 51 dive was an RAF test in which a MK IV was at .82-.85 M (instrumentation a little fuzzy) and the aircraft had so many wringled panels and fastners fail that the a/c was written off. That was Far above the Placard speed.

But hey, the P-40 was such an under appreciated wonder plane that it could out dive most early jets.

How do we know? because war time propaganda newsreels tell us so

 

[Schweik]

There are also 12 lost to unknown causes here

Yes but on the other hand, in Shores MAW you can see that probably a third to half of the combat losses were due to flak (more to flak in 1944 as we previously discussed), and probably half of the "other" losses were on days when the Germans did not make any air to air claims. Engine trouble was mentioned frequently.

Another source posted by Eagledad in another thread gave 481 USAAF P-40 claims in the MTO.

The 592 number is the correct number. We may not know how many they actually shot down,* but we do know how many they claimed. My sources for 592 victory claims for USAAF P-40 units in the Med is from American Victory Roll page 111 and P-40 Warhawk Aces of the MTO (Osprey), page 87, which helpfully breaks down the victories by squadron. You can read it yourself here

S

*MAW gets us a little closer and can explain it for certain days but for some other days it's really impossible to tell who got what kill.

 

[Schweik]

How do we know? because war time propaganda newsreels tell us so

You have a history in our discussions in this forum of doubting any historical evidence which doesn't fit your own models of how things work. You do seem quite knowledgable on things like engines and superchargers, but am I supposed to trust your expertise on everything to do with the Air War over all other evidence ?

If you think this is so ludicrous, post some data that contradicts it.

All pilots who flew the P-40 noted it's high dive speed and in fact, diving out of combat (usually a vertical dive sometimes following Split S) became the standard escape maneuver both against Japanese and German fighters. I have never seen any mention of compressibility issues with the P-40 of the type encountered by the P-38. Have you? The only limit or issue described by pilots was either the need to use heavy rudder pressure to counteract the torque at high speeds, and / or the need to adjust trim settings quickly during dive and subsequent pull out.

I spoke to a pilot at an air show two months ago who told me he was making 400 mph in shallow dives during fly bys at the airshow, at 25" Hg and 2500 rpm no less (basically cruise settings) and he told me the fastest he'd flown that P-40N was 500 mph in a dive. And that is a 75 year old Warbird.

 

[Schweik]

Here is a record of the test, done at Wright field The pilots name was Bob or Robert Fausel, the aircraft was a P-40D.

He was apparently a test pilot on contract to Curtiss. This is a photo of him second from the left

Test & Research Pilots, Flight Test Engineers: Robert W. Fausel 1914-1998

Newspaper article

Madera Tribune 12 July 1941 — California Digital Newspaper Collection

 

[BiffF15]

You have a history in our discussions in this forum of doubting any historical evidence which doesn't fit your own models of how things work. You do seem quite knowledgable on things like engines and superchargers, but am I supposed to trust your expertise on everything to do with the Air War over all other evidence ?

If you think this is so ludicrous, post some data that contradicts it.

All pilots who flew the P-40 noted it's high dive speed and in fact, diving out of combat (usually a vertical dive sometimes following Split S) became the standard escape maneuver both against Japanese and German fighters. I have never seen any mention of compressibility issues with the P-40 of the type encountered by the P-38. Have you? The only limit or issue described by pilots was either the need to use heavy rudder pressure to counteract the torque at high speeds, and / or the need to adjust trim settings quickly during dive and subsequent pull out.

I spoke to a pilot at an air show two months ago who told me he was making 400 mph in shallow dives during fly bys at the airshow, at 25" Hg and 2500 rpm no less (basically cruise settings) and he told me the fastest he'd flown that P-40N was 500 mph in a dive. And that is a 75 year old Warbird.

Schweik,

To concur with SR6 I have also read many times about the airspeed indicators inaccuracies. I have also read where the Spit had the highest MachCrit of the WW2 fighters. It is very likely that Curtiss did not account for airspeed installation errors or inaccuracies for that newsreel clip.

The airspeed indicator probably indicated what they advertised, but that doesn't mean it was accurate.

Cheers,
Biff

 

[Schweik]

Schweik,

To concur with SR6 I have also read many times about the airspeed indicators inaccuracies. I have also read where the Spit had the highest MachCrit of the WW2 fighters. It is very likely that Curtiss did not account for airspeed installation errors or inaccuracies for that newsreel clip.

The airspeed indicator probably indicated what they advertised, but that doesn't mean it was accurate.

Cheers,
Biff

I agree 100% that 1930's - 1940's airspeed indicators were routinely way off, (I would assume modern ones are potentially better but you tell me) but presumably Curtiss engineers supervising the test were aware of it. Now it is also quite possible that 660 mph was one measure (IAS) and the TAS was known to be different, but they published the former instead for propaganda purposes, though I thought that IAS was usually lower than TAS depending on altitude and very generally speaking (though again, you tell me)

The only way to be sure would be to find the document of the test but googling failed for me, all I could determine was that the guy was a real test pilot and that they did do some kind of test at Wright field with a P-40D, which followed another previous test with a slightly lower speed result.

My point though was that the P-40 really didn't have any limits to dive speed apparently accept the dangers of approaching mach. I've yet to see any evidence to contradict that.

If anyone knows the real mach crit for any version of the P-40 please post it. The manual indicates a dive speed limit of 480 mph but that is obviously over-conservative as with so many other things in the manual.

S

 

[rochie]

AIr speed indicators were notoriously unreliable at higher than normal speeds. Many planes 'recorded' some astonishingly high dive speeds in WW II

Just for laughs figure it out. 661 mph at 5,000ft (got to leave room to pull out ) is Mach .884 at 10,000ft it is mach .899

From wike so......
on the Spitfire. ......

Beginning in late 1943, high-speed diving trials were undertaken at Farnborough to investigate the handling characteristics of aircraft travelling at speeds near the sound barrier (i.e., the onset of compressibility effects). Because it had the highest limiting Mach number of any aircraft at that time, a Spitfire XI was chosen to take part in these trials. Due to the high altitudes necessary for these dives, a fully feathering Rotol propeller was fitted to prevent overspeeding. During these trials, EN409, flown by Squadron Leader J. R. Tobin, reached 606 mph (975 km/h) (Mach 0.891) in a 45° dive.


In April 1944, the same aircraft suffered engine failure in another dive while being flown by Squadron Leader Anthony F. Martindale, Royal Air Force Volunteer Reserve, when the propeller and reduction gear broke off. The dive put the aircraft to Mach 0.92, the fastest ever recorded in a piston-engined aircraft, but when the propeller came off, the Spitfire, now tail-heavy, zoom-climbed back to altitude. Martindale blacked out under the 11 g loading, but when he resumed consciousness, he found the aircraft at about 40,000 feet with its (originally straight) wings now slightly swept back.[125] Martindale successfully glided the Spitfire 20 mi (32 km) back to the airfield and landed safely.[126] Martindale was awarded the Air Force Cross for his exploits.[127]

RAE Bedford (RAE) modified a Spitfire for high-speed testing of the stabilator (then known as the "flying tail") of the Miles M.52 supersonic research aircraft. RAE test pilot Eric Brown stated that he tested this successfully during October and November 1944, attaining Mach 0.86 in a dive.


Then look at all the troubles the P-38 and even the P-47 had with mach tuck.

or from Bill Marshall:
The fastest I Have ever heard of a 51 dive was an RAF test in which a MK IV was at .82-.85 M (instrumentation a little fuzzy) and the aircraft had so many wringled panels and fastners fail that the a/c was written off. That was Far above the Placard speed.

But hey, the P-40 was such an under appreciated wonder plane that it could out dive most early jets.

How do we know? because war time propaganda newsreels tell us so

also it should be noted that Martindale made a normal wheels down landing after all that drama, not bad for the fragile spitfire !

 

[GrauGeist]

If the P-40 was truly travelling at 661mph, it was already in a transonic envelope, which starts at Mach .72 (600mph).
Even the Me262 was limited to Mach .86 (659mph) because of transonic compression on control surfaces.

On 13 November 1942, two test pilots were said to have passed the speed of sound in dives from just under 50,000 feet in P-47Cs, reaching 725mph in their dives. However, in 1944, a P-47D made a power dive from 40,000 feet and the P-47 refused to go beyond Mach .86 even before hitting denser air at 20,000 (+/-) feet.

I have absolutely no doubt that the P-40's IAS was showing 600+ mph in a dive, but as the speeds increase, so does the pressure at the pitot head, giving a false reading.

 

[Dan Fahey]

DELETED Duplicate

 

[Dan Fahey]

Typhoons never got shoot up japanese twin bombers or other rather vulnerable targets in the CBI or South Pacific.
Typhoons also never got shoot up Macchi 200s, SM 79s Italian transports or JU 52s or Me 323s.
Germans for much of 1942 and 1943 didn't have to come and "play" with fighter sweeps over NW Europe unless they thought they had an actual advantage.

I really don't think the British got value for money from the TYphoon, mainly because of the Sabre engine. It's destructiveness as rocket firing airplane is vastly overblown. the 132 tank kills sometimes claimed was more like 6. The British (and the Allies) could probably have conducted the war with the Typhoon never having been built and would not have affected the outcome in any significant way. (assuming they built 3000 of a different plane)
But simplistic comparisons like number of planes shot down vs number of planes built really don't tell us much.

The P-40 Did affect the conduct of the war by being available in numbers when and where needed in 1941-42-43. However it's continued combat survivability had as much to do with it's opponents stumbling and dropping the ball/s than any great properties of the P-40 it self.

Interesting topic....The P40 was used in every Theater of War extensively and for a short while in England because the P40 had a much better range than any British Fighter. Typhoon/Tempest were coulda, shouda, woulda planes that took a while to sort out. The last version with a Sleeve Valve Radial proved to be the best solution.

The P40 was well sorted out with the P36 and that means a lot considering WW2 lasted about 10 years and development of reliable aircraft were at a premium. There were a lot of missed opportunities that prevented some planes from being more successful. Most could-would be sorted out over time. However the pressures of war just did not have a lot of time.

IMO the P40 was the best most versatile fighter we had. Used for just about every military situation from air superiority, ground attack, Recon and reasonable fighter to get skills up to speed. Logistics had a huge benefit as the US standardized on the 50 cal, fuels, and radios, parts.

I agree 100% that 1930's - 1940's airspeed indicators were routinely way off, (I would assume modern ones are potentially better but you tell me) but presumably Curtiss engineers supervising the test were aware of it. Now it is also quite possible that 660 mph was one measure (IAS) and the TAS was known to be different, but they published the former instead for propaganda purposes, though I thought that IAS was usually lower than TAS depending on altitude and very generally speaking (though again, you tell me)

The only way to be sure would be to find the document of the test but googling failed for me, all I could determine was that the guy was a real test pilot and that they did do some kind of test at Wright field with a P-40D, which followed another previous test with a slightly lower speed result.

My point though was that the P-40 really didn't have any limits to dive speed apparently accept the dangers of approaching mach. I've yet to see any evidence to contradict that.

If anyone knows the real mach crit for any version of the P-40 please post it. The manual indicates a dive speed limit of 480 mph but that is obviously over-conservative as with so many other things in the manual.

S

P40 required retrimming when it got into serious dive…. think it was neutral at about 250mph..

 

[Shortround6]

You have a history in our discussions in this forum of doubting any historical evidence which doesn't fit your own models of how things work. You do seem quite knowledgable on things like engines and superchargers, but am I supposed to trust your expertise on everything to do with the Air War over all other evidence ?

If you think this is so ludicrous, post some data that contradicts it.

All pilots who flew the P-40 noted it's high dive speed and in fact, diving out of combat (usually a vertical dive sometimes following Split S) became the standard escape maneuver both against Japanese and German fighters. I have never seen any mention of compressibility issues with the P-40 of the type encountered by the P-38. Have you? The only limit or issue described by pilots was either the need to use heavy rudder pressure to counteract the torque at high speeds, and / or the need to adjust trim settings quickly during dive and subsequent pull out.

I spoke to a pilot at an air show two months ago who told me he was making 400 mph in shallow dives during fly bys at the airshow, at 25" Hg and 2500 rpm no less (basically cruise settings) and he told me the fastest he'd flown that P-40N was 500 mph in a dive. And that is a 75 year old Warbird.

We are on other sides of the spectrum, you doubt anything that contradicts your own view of how things worked, even if your view contradicts physics.
Or you stretch and impose your view on an interview or quote that doesn't say exactly what you think it says.

I posted some data from the Spitfire that suggests that high mach number dives were rare and dangerous at speeds below the Curtiss claim. You choose to ignore it.
The Mach problems were barely known when this flight took place. And in many cases early pilots who ran into a problem were able to get out of it when the plane got into lower, thicker air and the plane slowed down. The P-40D was lucky it could high enough to get into trouble (slight exaggeration).
Now for your consideration the XF4U was undergoing trials at about this time and the navy was requiring that the plane do a vertical dive to a speed where the drag and power/gravity balanced out (a terminal velocity dive ). I can't remember if the Navy gave up or if the Corsair finally passed the test (it was the last Navy plane that they tried the test on) .
I would also note for newsreel/nespaper accuracy that the Hawker Hurricane I is credited with making a 400mph flight in 1938 (?). if you really want I may be able to find the date and pilots name, what nobody can find out is strength of the tailwind on that day.

Now since drag goes up with the square of the speed the drag at 661mph is 75% higher than the drag at 500mph. Just because a plane dived at 500mph in no way means it could hit 661mph.
Many planes will hit that drag limit, 1930s biplanes we just about all do it. the question is wither the plane in question will suffer structural failure or loss of control before it hits that drag limit.
I would also note that in the transonic speed range the simple drag formula no long applies,

Not all aircraft have quite the same curve but it is due to the rapid rise in drag (or pressure waves in the pitot tube) that many early dive speeds were off by so much.
Please note the chart is for the change in the coefficient of drag, not the change in the drag.
If your coefficient of drag is making a rapid change with increased speed at the same time that the drag is going up "normally" due to speed the combination is like hitting a wall.

Claiming the P-40 was exempt from this or could somehow make just about mach .9 in a dive is not facing facts.

 

[Schweik]

We are on other sides of the spectrum, you doubt anything that contradicts your own view of how things worked, even if your view contradicts physics.
Or you stretch and impose your view on an interview or quote that doesn't say exactly what you think it says.

It's funny - you might be describing your own posts here. The question generally is, what matters more, your theory or the data? You seem approach these things through your understanding of engineering and physics, which I suspect either has something to do with your work background or a major hobby you are into. I am into history, (in another field, WW2 aviation is just a hobby for me) and have published a few history articles in peer reviewed academic journals. In that realm, so to speak, the data rules, and the theories follow the data. If you try to push a theory that isn't supported in the data you will get annihilated. Many non historians bend or filter data to match their theories. Data that doesn't match is rejected as noise.

Which is why contrary to your accusation, I generally don't trust theories.

I have learned in 20 years of doing serious research, the theories fall short again and again and again. Imagine two points on a chalk board. You'll get one faction saying it represents a line going up, another faction insisting it can only be a line going down. Then a third data point appears - another dot. Now everyone has a new theory that the data indicates a triangle. Then there is a fourth point and now people bitterly argue if it's a square, or two triangles, and a conspiracy faction insists it's pentagram. Or whatever.

I think it's far better to trust the data, accept that you'll never know the whole picture, and be wary of becoming too enamored of your theories. The more invested you are in your theory the more you will resist new data points that contradict it, and the further away your understanding will drift from what the data actually says. Be extra wary of assuming that you understand the systems and the material physical realities of another time period under conditions you didn't actually live through. Theories should always be provisional and subject to rapid change. Even if your model is right, it's always far more likely that you are missing some element of data that would account for what you see in the data.

When it comes to the history of this aircraft, the amount of data that has to be filtered out to support the old theory has begun to outweigh the data which actually supports it. That is all I have been pointing out.

And the response in this specific comparison between two aircraft (the result of a challenge from another thread) is a series of diversions to explain why P-40F pilots made so many more victory claims than the Typhoon, (and seemed to like their aircraft better), each easily debunked.

• They made a lot more P-40s (but not of this version - only 2000 P-40F/L vs 3000 Typhoons)
• The P-40 faced weak opposition consisting of Bombers and obsolete Japanese planes (not true - and most of the victories by P-40Fs were against fighters, and mostly Bf 109s)
• But Macchi 202s were second rate! (Not true either, or certainly an outlier position)
• The Typhoon didn't fight for as long so had fewer opportunities (P-40 F/L were in combat from roughly August 1942 to Sept 1944, but 90% of their victory claims were before Sept 43.)
• The P-40 fought in multiple Theaters (but not this version - 17 out of 18 squadrons using the plane were in the Med)
• The Typhoon shot down Fw 190s and the P-40 couldn't (P-40's clearly did)

Right now you are arguing about whether a P-40 could hit mach 0.9 or mach 0.88 or what, when the real issue is pretty clear - from Allied and Axis pilot testimony it had one of the fastest dive speeds of the war. Beyond that we don't know the details until somebody posts them. It was clearly fast enough in a dive to catch Fw 190s and that's pretty fast. And there is no evidence so far that I've seen showing that the Typhoon had a faster dive speed, in fact given the problems with the tail, control surface flutter and structural failures, I suspect it didn't but I won't insist on it because I don't actually know.

 

[Schweik]

I should add, Shortround, that your understanding of the physics and engineering is useful, and has been helpful to me and I'm certain many others in these discussions. Your posts have given me valuable insights for example about how superchargers work. I just think you have to be careful with the assumption that provisional physics models, even good ones, trump other sources. You have to remain open to data. Even if you think it may be 'noise' (and some of it obviously is like your 400 mph Hurricane I) you need to keep track of it because there can come a point where the 'noise' starts to outweigh what we thought was the 'good' data and then it's time to re-evaluate your model.

 

[Stig1207]

Yes but on the other hand, in Shores MAW you can see that probably a third to half of the combat losses were due to flak (more to flak in 1944 as we previously discussed), and probably half of the "other" losses were on days when the Germans did not make any air to air claims. Engine trouble was mentioned frequently.

Did you read the small print above the tables?


The 592 number is the correct number. We may not know how many they actually shot down,* but we do know how many they claimed. My sources for 592 victory claims for USAAF P-40 units in the Med is from American Victory Roll page 111 and P-40 Warhawk Aces of the MTO (Osprey), page 87, which helpfully breaks down the victories by squadron. You can read it yourself here

S

*MAW gets us a little closer and can explain it for certain days but for some other days it's really impossible to tell who got what kill.

The 481 number is from Ray Wagner's American Combat Planes . Interestingly, if you add up the figures for sorties, victories and losses for fighters in the ETO/ MTO as presented in the USAAF Statistical Digest, they match Wagners' very well.
We can agree on not knowing how many they actually shot down; I, however, don't see why 592 mentioned in some books should be more likely than the 481 mentioned in another.

 

[Shortround6]

I should add, Shortround, that your understanding of the physics and engineering is useful, and has been helpful to me and I'm certain many others in these discussions. Your posts have given me valuable insights for example about how superchargers work. I just think you have to be careful with the assumption that provisional physics models, even good ones, trump other sources. You have to remain open to data. Even if you think it may be 'noise' (and some of it obviously is like your 400 mph Hurricane I) you need to keep track of it because there can come a point where the 'noise' starts to outweigh what we thought was the 'good' data and then it's time to re-evaluate your model.

The 400 mph hurricane was simply to show that newspaper headlines or movie newsreels are rather unreliable data sources. When such "data points" conflict with later research or information which should we trust?
Not just the P-40 but many other earlier aircraft posted very high dive speeds, but such dive speeds could not be repeated in later tests with more specialized instruments which leaves us where?
Trying to fit newsreel propaganda into our data set?

Or just ignoring it.

Now I have never said that the P-40 was not a good diver. But being a good diving propeller plane is very far from going faster (in a dive) than many early jets isn't it?

The 661mph dive of the P-40 is just noise.

The airspeed limit on the P-40D/E was 485mph indicated on page 22 of the April 1941 manual (revised Sept 5th 1941). In the 1943 manual is says 480mph indicated (page 61) and says that 5-8,000ft are needed to pull out of a high speed dive. Also on page 61 is a warning that vertical dives starting above 20,000ft are not recommended because of the danger of compressibility.
It doesn't say what the dangers are or what to do about them and it doesn't say that such dives are prohibited, "not recommended" is pretty weak language.

I am not going to worry about a 5mph difference in the manuals. Pick what you want. Trying to read a gauge to 5 mph out 480mph in a high speed dive (ground coming up at 700 feet per second) with the plane trying to roll to the right is a finer distinction that I would ever try to make.

 

[Schweik]

The 481 number is from Ray Wagner's American Combat Planes . Interestingly, if you add up the figures for sorties, victories and losses for fighters in the ETO/ MTO as presented in the USAAF Statistical Digest, they match Wagners' very well.
We can agree on not knowing how many they actually shot down; I, however, don't see why 592 mentioned in some books should be more likely than the 481 mentioned in another.

Well, it seems more likely that Ray Wagner left some out than that Dr Wolf (American Victory Roll) or mr Moleseworth (Osprey) - and various other sources made them up, in a nutshell. Why would they? I think it's wishful thinking on your part.

 

[Schweik]

The 661mph dive of the P-40 is just noise.

The airspeed limit on the P-40D/E was 485mph indicated on page 22 of the April 1941 manual (revised Sept 5th 1941). In the 1943 manual is says 480mph indicated (page 61) and says that 5-8,000ft are needed to pull out of a high speed dive. Also on page 61 is a warning that vertical dives starting above 20,000ft are not recommended because of the danger of compressibility.
It doesn't say what the dangers are or what to do about them and it doesn't say that such dives are prohibited, "not recommended" is pretty weak language.

I am not going to worry about a 5mph difference in the manuals. Pick what you want. Trying to read a gauge to 5 mph out 480mph in a high speed dive (ground coming up at 700 feet per second) with the plane trying to roll to the right is a finer distinction that I would ever try to make.

Maybe 661 is noise but I don't believe the limit was the one from the manual, either one, because pilot after pilot reported diving at over 500 mph... including one I spoke to personally.

 

[Kevin J]

Maybe 661 is noise but I don't believe the limit was the one from the manual, either one, because pilot after pilot reported diving at over 500 mph... including one I spoke to personally.

I recall reading somewhere that the 480/485 mph speed limit was that recommended by Curtiss and that the P-40 could be flown up to another 30 mph faster in a dive. I assume this resulted in damage. I guess this is like the recommended max boost settings to the V-1710-39/63, which could be exceeded but might cause damage. I guess if you want to survive you exceed the limits set on dive and engine power.

 

[Shortround6]

Maybe 661 is noise but I don't believe the limit was the one from the manual, either one, because pilot after pilot reported diving at over 500 mph... including one I spoke to personally.

I would say that the 485 limit in the manual probably leaves a margin of error. How great that margin is on any given day may vary with the temperature/air pressure that day, the exact rigging/alignment of the aircraft and perhaps the pilots flying technique.
I certainly don't believe that hitting 486mph is going to result in the instant destruction of the aircraft or unrecoverable loss of control.

In an unrelated but somewhat parallel illustration I used to do quite a bit of target shooting and hand loading. I believe the loading manuals when they tell you to only a maximum weight of powder in a certain application. They too are giving themselves a safety margin BUT I was once at a match were the fellow I was squaded with (he shot while I scored and then we went to the pits to operate the target) was using a rifle chambered for a round similar to mine so we discussed loads. I was about 2 grains under max for a particular powder and he was about 2 grains over (on a high 40s powder charge) so the percentage wasn't great. In the morning (upstate New York in the summer) he had no troubles. In after noon with sun right overhead and hotter temperatures he got off 3 rounds out of 22. each cartridge was harder to extract< I was helping so he would have to get up out the prone position but on the 3rd round bare hands wouldn't do it. A plastic box hitting the bolt handle wouldn't do and he resorted to a rock wrapped in cloth to beat the bolt handle open on a custom built target rifle.
What would have happened if he had been shooting in Arizona or New Mexico I have no idea. The temperature change was enough to push the chamber pressure from "it works" (but may not be safe) to it doesn't work and IS decidedly unsafe. A manufacturer's recommendation/limit has to provide enough of a safety margin to cover most foreseeable circumstances.

The dive speed recommendations/limits in the P-40 manuals are a blanket limit, they don't specify gross weight (or CG location) or altitude or temperature pressure.
But then most or all of the other pilots manuals I have seen use a blanket statement too. They may have a different limit for under ordinance or stores, Some planes have the same limit for bombs/drop tanks and some have different ones but I don't think I have ever seen one that breaks it down by the size/weight of the bombs, doesn't mean there isn't such a manual.

I would note that the 1943 manual suggests pilots in training limit their dive speed to 350mph indicated and says that the short tail planes need more pressure on the controls than the long tail planes.